Sr and Nd isotopes as tracers in pedogenic studies. Evidence for Saharan dust contribution to the soils of Muravera (Sardinia, Italy)

Sr and Nd isotopes were applied to 5 soil profiles from the Muravera area, in south-eastern Sardinia.All the soils, which have developed during the Quaternary on the Lower Paleozoic metamorphic base-ment except for one on Eocene carbonates, are located far from major sources of pollution. Therefore,they are suitable for testing pedogenic processes and geochemical evolution to benefit for environmentalstudies.The Sr isotopic ratios range largely (87Sr = 1.7–65.9‰), even in each soil profile. In particular, theobserved increase of 87Sr with depth in the most of the metamorphic rock-based soils can be accountedfor by the downward decrease of Sr contributions from organic matter and Saharan dust, both display-ing lower isotopic ratios than the soil bedrocks. The carbonate rock-based soil exhibits 87Sr higher(1.7–18.1‰) than the bedrock, indicating a significant contribution of radiogenic Sr from the siliciclasticfraction of the soil, and probably from dust input. The Nd isotopic ratios are slightly variable throughthe profiles (εNdfrom −7.8 to −14.5), confirming little mobility of Nd and Sm during the pedogenesis.Among the minerals present in the soils, phosphates, albite, and calcite are those important in providinglow radiogenic Sr and Nd to organic matter of the soils.Lastly, this isotopic study has in particular allowed for evaluating the potential proportion of contribu-tion of Saharan dust to south-eastern Sardinia, thus corroborating the findings of other studies related tosoils from the central-western Mediterranean.